Lead-free insulation compositions containing metallocene polymers

Abstract

Novel additive systems for lead-free filled cable insulation are disclosed. These systems provide improved electrical and mechanical properties. The base polymer may be metallocene based, non metallocene based or combinations thereof. The additives may contain one or more hindered amine light stabilizers, mercapto compounds, and optionally, amine antioxidants.

Description

[0001] This claims priority under 35 U.S.C. §119(e) to Ser. No. 60 / 729,735, filed Oct. 25, 2005.FIELD OF THE INVENTION [0002] The invention relates to lead-free insulation compositions for electric power cables having (a) a base polymer comprising either (i) at least one metallocene polymer, or (ii) at least one non-metallocene polymer or (iii) a combination thereof; (b) a filler; and (c) an additive comprising either (i) at least one hindered amine light stabilizer, or (ii) at least one mercapto compound, or (iii) a combination thereof. BACKGROUND OF THE INVENTION [0003] Typical power cables generally have one or more conductors in a core that is surrounded by several layers that can include: a first polymeric semiconducting shield layer, a polymeric insulating layer, a second polymeric semiconducting shield layer, a metallic tape shield and a polymeric jacket. [0004] Polymeric materials have been utilized in the past as electrical insulating and semiconducting shield materials for...

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Benefits of technology

[0025] The invention provides an additive system that improves the per...

Problems solved by technology

One major type of failure that polymeric power cable insulation can undergo is the phenomenon known as treeing.

In solid organic dielectrics, treeing is the most likely mechanism of electrical failures, which do not occur catastrophically, but rather appear to be the result of a more lengthy process.

The damage, which results from the application of moderate alternating current voltages to the electrode/insulation interfaces, which can contain imperfections, is commercially significant.

The failure mechanism involves actual breakdown of the modular structure of the dielectric material, perhaps by electron bombardment.

Buried power cables are especially vulnerable to water treeing.

However, polyethylene homopolymers are very prone to water treeing, especially toward the upper end of the medium-voltage range.

However, these residues are eventually lost at most temperatures where electrical power cable is used.

Unfortunately, while the fillers utilized in EPR may help prevent treeing, the filled EPR will generally have poorer dielectric properties, i.e. a poorer dielectric constant and a poor power factor.

Thus, both polyethylenes and EPR have serious limitations as an electrical insulator in cabl...

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